
NMR in Biomedicine
SCOPUS (1988-2023)SCIE-ISI
1099-1492
0952-3480
Anh Quốc
Cơ quản chủ quản: John Wiley and Sons Ltd , WILEY
Các bài báo tiêu biểu
Anisotropic water diffusion in neural fibres such as nerve, white matter in spinal cord, or white matter in brain forms the basis for the utilization of diffusion tensor imaging (DTI) to track fibre pathways. The fact that water diffusion is sensitive to the underlying tissue microstructure provides a unique method of assessing the orientation and integrity of these neural fibres, which may be useful in assessing a number of neurological disorders. The purpose of this review is to characterize the relationship of nuclear magnetic resonance measurements of water diffusion and its anisotropy (i.e. directional dependence) with the underlying microstructure of neural fibres. The emphasis of the review will be on model neurological systems both
The state of the art of reconstruction of the axonal tracts in the central nervous system (CNS) using diffusion tensor imaging (DTI) is reviewed. This relatively new technique has generated much enthusiasm and high expectations because it presently is the only approach available to non‐invasively study the three‐dimensional architecture of white matter tracts. While there is no doubt that DTI fiber tracking is providing exciting new opportunities to study CNS anatomy, it is very important to understand its limitations. In this review we therefore assess the basic principles and the assumptions that need to be made for each step of the study, including both data acquisition and the elaborate fiber reconstruction algorithms. Special attention is paid to situations where complications may arise, and possible solutions are reviewed. Validation issues and potential future directions and improvements are also discussed. Copyright © 2002 John Wiley & Sons, Ltd.
The LCModel method analyzes an alanine aspartate creatine γ‐aminobutyric acid glucose glutamine glutamate glycerophosphocholine glutathione lactate phosphocholine phosphocreatine phosphoethanolamine signal‐to‐noise ratio taurine.
We review several methods that have been developed to infer microstructural and physiological information about isotropic and anisotropic tissues from diffusion weighted images (DWIs). These include Diffusion Imaging (DI), Diffusion Tensor Imaging (DTI), isotropically weighted imaging, and q‐space imaging. Just as DI provides useful information about molecular displacements in one dimension with which to characterize diffusion in isotropic tissues, DTI provides information about molecular displacements in three dimensions needed to characterize diffusion is anisotropic tissues. DTI also furnishes scalar parameters that behave like quantitative histological or physiological‘stains’ for different features of diffusion. These include Trace(D), which is related to the mean diffusivity, and a family of parameters derived from the diffusion tensor, D, which characterize different features of anisotropic diffusion. Simple thought experiments and geometrical constructs, such as the diffusion ellipsoid, can be used to understand water diffusion in isotropic and anisotropic media, and the NMR experiments used to characterize it.
Molecular and cellular MR imaging is a rapidly growing field that aims to visualize targeted macromolecules or cells in living organisms. In order to provide a different signal intensity of the target, gadolinium‐based MR contrast agents can be employed although they suffer from an inherent high threshold of detectability. Superparamagnetic iron oxide (SPIO) particles can be detected at micromolar concentrations of iron, and offer sufficient sensitivity for
This article treats the theoretical underpinnings of diffusion‐tensor magnetic resonance imaging (DT‐MRI), as well as experimental design and data analysis issues. We review the mathematical model underlying DT‐MRI, discuss the quantitative parameters that are derived from the measured effective diffusion tensor, and describe artifacts thet arise in typical DT‐MRI acquisitions. We also discuss difficulties in identifying appropriate models to describe water diffusion in heterogeneous tissues, as well as in interpreting experimental data obtained in such issues. Finally, we describe new statistical methods that have been developed to analyse DT‐MRI data, and their potential uses in clinical and multi‐site studies. Copyright © 2002 John Wiley & Sons, Ltd.
Manganese‐enhanced MRI (MEMRI) is being increasingly used for MRI in animals due to the unique
Diffusion NMR is the only method available today that noninvasively provides information on molecular displacements over distances comparable to cell dimensions. This information can be used to infer tissue microstructure and microdynamics. However, data may be fairly difficult to interpret in biological tissues which differ markedly from the theoretical “infinite isotrope medium”, as many factors may affect the NMR signal. The object of this paper is to analyze the expected effects of temperature, restriction, hindrance, membrane permeability, anisotropy and tissue inhomogeneity on the diffusion measurements. Powerful methods, such as q‐space imaging, diffusion tensor imaging and diffusion spectroscopy of metabolites further enhance the specificity of the information obtained from diffusion NMR experiments.
Quantitative susceptibility mapping (QSM) is a recently developed MRI technique that provides a quantitative measure of tissue magnetic susceptibility. To compute tissue magnetic susceptibilities based on gradient echoes, QSM requires reliable unwrapping of the measured phase images and removal of contributions caused by background susceptibilities. Typically, the two steps are performed separately. Here, we present a method that simultaneously performs phase unwrapping and HARmonic (background) PhasE REmovaL using the LAplacian operator (HARPERELLA). Both numerical simulations and